Humidifiers that make use of a float switch will de-energize a fan assembly and/or indicate an out-of-water condition as soon as the water level is insufficient to create enough buoyancy to activate the float switch. The float switch generally de-energizes the fan assembly well before all of the water is evaporated from the water reservoir of the humidifier. A wet or damp wick likely sits in standing water for an extended duration of time if water remains in the reservoir and on the wick after the fan is turned off. The damp reservoir and wick have the potential to create a stale humidifier.
Briefly stated, the present invention is an evaporative humidifier. The humidifier includes a housing, a fan assembly, a wick assembly, a first humidity sensor, a second humidity sensor, and a controller. The housing has an air inlet, an air outlet, and a reservoir for holding water. The fan assembly creates an airflow through the housing from the inlet to the outlet. The wick assembly is in fluid communication with the water in the reservoir and extends into the airflow within the housing for adding moisture to the airflow. The first humidity sensor measures an ambient air relative humidity and produces a first signal corresponding to the ambient air relative humidity. The second humidity sensor measures an outlet air humidity and produces a second signal corresponding to the outlet air humidity. The controller is in electrical communication with the first and second humidity sensors, receives the first and second signals, and performs calculations to produce an output signal for controlling the operation of the humidifier.